Non-cardiac chest pain (NCCP), defined as intermittent chest pain inpatients with no evidence of heart disease, affects over 180,000 new patients per year. The cause of NCCP remains unknown though the esophagus has been implicated in up to one third of patients. Scientists have traditionally felt that NCCP is related to spasm of the esophagus, acid reflux disease, or psychosocial factors. More recently, investigators have suggested that "hypersensitivity" of the nervous system may play a role in the development of NCCP. Patients with NCCP have been found to experience pain at lower levels of balloon inflation in the esophagus than healthy persons. Positron emission tomography (PET) allows the mapping of brain structures occurring in response to various types of stimulation. We intend to use PET scanning to evaluate the brain structures responsible for the sensation of heat stimulation of the skin and balloon stimulation of the esophagus in a group of healthy volunteers.